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Biomedical subjects

Kuni Ohtomo

Publications and source records attributed to Kuni Ohtomo.

At least 73 records · Page 4Linked to original sources
PubMed2004

Prolonged renal parenchymal retention of 99mTc mercaptoacetyltriglycine after nephron-sparing surgery.

OBJECTIVE: Nephron-sparing surgery is a treatment in which a part of a diseased kidney is resected and some parenchyma of the kidney is spared. Impairment of spared renal parenchyma after the surgery may cause prolonged prarenchymal retention in renal scintigraphy with Tc mercaptoacetyltriglycine (Tc-MAG3). The aim of this study was to determine whether or not parenchymal retention of Tc-MAG3 is prolonged after nephron-sparing surgery. METHODS: Twenty-two patients underwent a total of 29 Tc-MAG3 studies within 1 year after nephron-sparing surgery. In 17 patients (23 examinations) who had bilateral kidneys, the presence of diffuse prolongation of parenchymal retention was determined for the operated kidney. In all patients, the presence of regional prolongation around the surgical margin was assessed. RESULTS: Diffuse prolongation was observed in four of 10 examinations performed within 1 month after surgery and in none of 13 examinations performed later than 1 month after surgery. Regional prolongation was shown in 10 of 14 examinations performed within 1 month after surgery and in three of 15 examinations performed later than 1 month after surgery. In five patients who were studied both prior to and later than 1 month after surgery, regional prolongation was noted on the first study. On the second study, regional prolongation was improved and initial renal uptake around the surgical margin was intensified. CONCLUSIONS: Renal parenchymal retention of Tc-MAG3 is frequently prolonged in the early period after nephron-sparing surgery. Renal scintigraphy with Tc-MAG3 may aid in characterizing acute renal damage after nephron-sparing surgery.

Adolescent↗
PubMed2004

Carvedilol therapy improved left ventricular function in a patient with arrhythmogenic right ventricular cardiomyopathy.

An asymptomatic 35 year-old man was referred to our hospital because of abnormal ECG findings. The ECG showed complete right bundle branch block and left anterior hemiblock. Echocardiography revealed a moderately enlarged right ventricle (RV) and an apical aneurysm. RV wall motion showed diffusely moderate impairment, while the systolic function of the left ventricle (LV) was slightly decreased. The ejection fractions (EF) of the RV and LV were calculated as 28.1% and 41.9% by Simpson's method using multiple cardiac computed tomography (CT) scans. A 24 hour ambulatory ECG showed only 372 single premature ventricular contractions (PVC). Cardiac catheterizaion revealed that the RV was enlarged with prominent trabeculation and decreased motion. In an electrophysiologic study, neither electrical stimulation of the RV nor electrical stimulation plus isoproterenol infusion could induce ventricular tachycardia. Pathological examination of a biopsy from the interventricular septum of the RV revealed fibrofatty change in the myocardium. Based on these results, we made a diagnosis of arrhythmogenic right ventriclular cardiomyopathy (ARVC) and administered 5 mg of carvedilol. Sixty days after the initiation of carvedilol therapy, we performed repeat cardiac CT. The EF of the LV was markedly improved from 41.9% to 62.0%, although the EF of the RV was not changed. The number of PVCs showed no change. This case suggests that carvedilol is not only useful for controlling arrhythmia but also for improving left ventriclular function in some patients with ARVC. Sympathetic overactivity is reported to cause sudden death, so carvedilol may be a first-line drug for some patients with ARVC.

Adrenergic beta-Antagonists↗
PubMed2004

Radiosensitization by hyperthermia in the chicken B-lymphocyte cell line DT40 and its derivatives lacking nonhomologous end joining and/or homologous recombination pathways of DNA double-strand break repair.

Hyperthermia has a radiosensitizing effect, which is one of the most important biological bases for its use in cancer therapy with radiation. Although the mechanism of this effect has not been clarified in molecular terms, possible involvement of either one or both of two major DNA double-strand break (DSB) repair pathways, i.e. nonhomologous end joining (NHEJ) and homologous recombination (HR), has been speculated. To test this possibility, we examined cells of the chicken B-lymphocyte cell line DT40 and its derivatives lacking NHEJ and/or HR: KU70(-/-), DNA-PKcs(-/-/-), RAD54(-/-) and KU70(-/-)/RAD54(-/-). Radiosensitization by hyperthermia could be seen in all of the mutants, including KU70(-/-)/RAD54(-/-), which lacked both NHEJ and HR. Therefore, radiosensitization by hyperthermia cannot be explained simply by its inhibitory effects, if any, on NHEJ and/or HR alone. However, in NHEJ-defective KU70(-/-) and DNA-PKcs(-/-/-), consisting of two subpopulations with distinct radiosensitivity, the radiosensitive subpopulation, which is considered to be cells in G(1) and early S, was not sensitized. Substantial sensitization was seen only in the radioresistant subpopulation, which is considered to be cells in late S and G(2), capable of repairing DSBs through HR. This observation did not exclude possible involvement of NHEJ in G(1) and early S phase and also suggested inhibitory effects of hyperthermia on HR. Thus partial contribution of NHEJ and HR in radiosensitization by hyperthermia, especially that depending on the cell cycle stage, remains to be considered.

Animals↗
PubMed2004

[Distinguishing between occluded and low-flow vessels with PROPELLER DWI sequence: a phantom study].

PURPOSE: To evaluate the ability of periodically rotated overlapping parallel lines with enhanced reconstruction diffusion-weighted imaging (PROPELLER DWI) to distinguish between vessel occlusion and slow flow. MATERIALS AND METHODS: Using a flow phantom with various velocities (1.37 to 11.1 cm/s), the signal-intensity ratios of the phantom, with the intensity of no flow as baseline, were measured using the following imaging sequences: PROPELLER DWI, spin-echo T1-weighted imaging (SE T1WI), fast-spin-echo T2-weighted imaging (FSE T2WI), two-dimensional phase-contrast imaging (2D PC), and two-dimensional time-of-flight imaging (2D TOF). The b-factor of PROPELLER DWI was varied from 0 to 1000 s/mm(2). The velocity encoding of 2D PC was varied from 2 to 30 cm/s. RESULTS: At the lowest flow velocity (1.37 cm/s) , the signal-intensity ratio was 0.0075 for PROPELLER DWI (b-factor=1000 s/mm(2)), 1.8 for SE T1WI, 0.67 for FSE T2WI, 11 for 2D PC (velocity encoding=2 cm/s), and 1.4 for 2D TOF. The signal-intensity ratio was smallest for PROPELLER DWI, even when the reciprocals of the signal-intensity ratio of 2D PC or 2D TOF were considered. CONCLUSION: The results indicate that PROPELLER DWI provides the best signal intensity-ratio between vessel occlusion and slow flow. Although DWI with single-shot echo-planar imaging (EPI) or multi-shot EPI may have similarly high sensitivity for slow flow, these sequences do not have high spatial resolution or robustness to susceptibility artifacts. PROPELLER DWI would be a better choice for distinguishing between occluded and low-velocity arteries in the skull base or parasellar regions.

Blood Flow Velocity↗
PubMed2004

[Imaging characteristics of PROPELLER T2-weighted imaging].

As the PROPELLER sequence is a combination of the radial scan and fast-spin-echo (FSE) sequence, it can be considered an FSE sequence with a motion correlation. However, there are some differences between PROPELLER and FSE owing to differences in k-space trajectory. We clarified the imaging characteristics of PROPELLER T2-weighted imaging (T2WI) for different parameters in comparison with usual FSE T2WI. When the same parameters were used, PROPELLER T2WI showed a higher signal-to-noise ratio (SNR) and lower spatial resolution than usual FSE. Effective echo time (TE) changed with different echo train lengths (ETL) or different bandwidths on PROPELLER, and imaging contrast changed accordingly to be more effective.

Artifacts↗
PubMed2004

[Principles of diffusion-weighted MR imaging and application to clinical neurology].

Diffusion-weighted Imaging (DWI) is a advantageous method for early detection of cerebral ischemia. DWI with echo-planar sequence (EP-DWI) offers multisectional images sensitive to cytotoxic edema in a very short aquisition time and is almost free from motion artifact. However, the susceptibility artifacts and low spatial resolution of EP-DWI must be improved. In estimation of DWI, influence of T2 must be considered, because DWI is almost always based on T2-weighted imaging. DWI is applied to other cerebral disorders such as degenerative and demyelinating disease, infectious disease, tumors or so. In order to demonstrate water diffusion precisely, diffusion tensor imaging (DTI) must be introduced and applied to anisotropy indices such as fractional anisotropy (FA) and depiction of neurofiber direction, tractography. Measurements of FA in various degenerative diseases may contribute to differentiation in normal appearing white matter. Diffusion tensor tractography may provide more information about relationship of major white matter tract such as corticospinal tract with brain lesion. Furthermore, DWI and DTI are expected to demonstrate diffusion of protons of aminoacids such as choline, creatine, NAA and provide more pertinent information of regional pathologic state of the brain in future.

Animals↗
PubMed2003

Development of intraarterial contrast-enhanced 2D MRDSA with a 0.3 tesla open MRI system.

PURPOSE: The purpose of this study was to develop a new technique for a high temporal resolution two-dimensional MR digital subtraction angiography (2D MRDSA) sequence under intraarterial injection of contrast material to permit the visualization of vascular anatomy and hemodynamics. METHODS: 2D MRDSA was imaged on a 0.3T open MR scanner with a T(1)-weighted fast gradient echo sequence. The phantom study examined vials containing gadolinium (Gd) solutions ranging in concentration from 0.5 mmol/L to 100 mmol/L. Repetition time and echo time were fixed at minimal values in order to achieve high temporal resolution, and only the flip angle was changed in 10-degree increments between 10 and 90 degrees. The in vivo study examined a brachial artery of a human volunteer. MRDSA images were acquired continuously during intraarterial injections of Gd solutions ranging in concentration from 0.5 mmol/L to 100 mmol/L. The subtracted images were displayed on the monitor in real time at a frame rate of one frame per second and evaluated to determine the optimal concentration of contrast material. RESULTS: In the phantom study, a 10-mmol/L Gd concentration with a flip angle of 50 degrees -90 degrees and a 25-mmol/L Gd concentration with a flip angle of 60 degrees -90 degrees showed high signal-to-noise ratios. In the human brachial artery experiment, the forearm arteries were well visualized when solutions of 5-50 mmol/L Gd concentration were used. The 10- and 25-mmol/L Gd concentrations were considered optimal. The palmar digital arteries were also visualized. Higher Gd concentrations showed a paradoxical signal increase when diluted by blood. CONCLUSION: We successfully developed an intraarterial contrast-enhanced 2D MRDSA sequence. With appropriate settings of imaging parameters and Gd concentrations, we obtained acceptable vessel visualization in the human study. The low Gd concentration for optimal visualization permits repeated intraarterial injections. This technique can be a useful tool for investigating the vascular anatomy and hemodynamics required for MR-guided vascular interventions.

Adult↗
PubMed2003

Dynamic conical conformal radiotherapy using a C-arm-mounted accelerator: dose distribution and clinical application.

PURPOSE: The aim of this study was to solve anisotropy in the dose distributions from rotational conformal radiotherapy (RCRT) by using a C-arm-mounted accelerator. MATERIALS AND METHODS: The linac head was designed to move along the C-arm with a maximum angle of 60 degrees (from a vertical position toward the gantry). Simultaneous rotation of the gantry creates a dynamic conical irradiation technique. Dynamic conical conformal radiation therapy (Dyconic CRT) was developed by combining the technique with continuous motion of a multileaf collimator. Dose distributions were measured in phantoms using film densitometry and compared with conventional RCRT. Dose distributions in actual radiation therapy patients are also presented. RESULTS: Dyconic CRT enabled the precise delivery of noncoplanar beams without rotating the table. The measurements showed that three-dimensionally isotropic dose falloff was achieved with Dyconic CRT. Dose inhomogeneity in the sagittal direction with Dyconic CRT was compensated for by use of wedge filters. CONCLUSIONS: The drawbacks of the dose distributions produced by RCRT were overcome with the use of Dyconic CRT.

Dose-Response Relationship, Radiation↗
PubMed2003

Feasibility of a curvature-based enhanced display system for detecting cerebral aneurysms in MR angiography.

PURPOSE: To assess the feasibility of a curvature-based enhanced display system for detecting cerebral aneurysms in MR angiography. METHODS: MR angiography studies of 18 patients (eight male and 10 female, average age 65.7, age range 50 to 75 years old) with 23 known aneurysms were evaluated with a curvature-based display system. The two curvature features-the volumetric shape index and curvedness values-were calculated at each voxel. These were displayed independently on a workstation, overlaid on volume-rendered images. Two neuroradiologists evaluated the images for visibility and diagnosis of the cerebral aneurysms. The diagnostic results were compared with the original reports. RESULTS: The calculation time for each curvature index was 30 to 40 s for 120 to 140 slices of original MR angiography data. Shape index images emphasized smooth and round aneurysms more than aneurysms with irregular surfaces. Curvedness images revealed aneurysms well when the aneurysms had diameters that differed from those of the surrounding vessels. The computer-assisted-detection method detected 24 aneurysms, three of which were not pointed out in the initial report. CONCLUSION: Our results show that the curvature-based display system we have developed is feasible and that it may help to detect small aneurysms that are prone to be overlooked in routine readings.

Aged↗
PubMed2003

Biliary motor function in gallstone patients evaluated by fatty-meal MR cholangiography.

PURPOSE: To investigate the possibility of evaluating biliary motor function with magnetic resonance cholangiography (MRC). MATERIALS AND METHODS: Twenty patients with gallstones and 30 control subjects were studied using fatty-meal MRC. After baseline MRC, they were encouraged to drink 250 mL of milk and underwent postprandial MRC every 10 minutes for 60 minutes. Postprandial changes in gallbladder volume and the diameter of the common duct were assessed as indicators of gallbladder contractility and biliary obstruction, respectively. Postprandial dilatation at 60 minutes was considered indicative of persistent biliary obstruction. RESULTS: Gallbladder ejection fraction was calculated at 66.0% +/- 12.2% (range, 40.3%-88.6%) in the controls. Gallbladder volume expressed as a percentage of the baseline value was significantly larger at 20-60 minutes in the gallstone patients than in the controls. Gallbladder ejection fraction varied widely (mean, 46.4% +/- 24.4%; range, 2.8%-81.5%) and was significantly reduced in comparison with that of the controls (P < 0.01). In two gallstone patients with co-existing ductal stones, transient postprandial dilatation associated with ampullary impaction was observed. Persistent biliary obstruction was not indicated in any subjects. CONCLUSION: The results of this study suggest the feasibility of fatty-meal MRC, as well as its potential for evaluating biliary motor function.

Adult↗
PubMed2003

MR imaging of ischemic penumbra.

Cerebral ischemic stroke is one of the most fatal diseases despite current advances in medical science. Recent demonstration of efficacy using intravenous and intra-arterial thrombolysis demands therapeutic intervention tailored to the physiologic state of the individual tissue and stratification of patients according to the potential risks for therapies. In such an era, the role of the neuroimaging becomes increasingly important to evaluate the extent and location of tissues at risk of infarction (ischemic penumbra), to distinguish it from unsalvageable infarcted tissues or doomed hemorrhagic parenchyma. In this review, we present briefly the current role and limitation of computed tomography and conventional magnetic resonance imaging (MRI). We also present the possible applications of advanced MR techniques, such as diffusion and perfusion imaging, concentrating on the delineation or detection of ischemic penumbra.

Brain Ischemia↗
PubMed2003

Nuclear medical PET-study in the causal relationship between mastication and brain function in human evolutionary and developmental processes.

The principal author (Kubote 1995, 1997, 1998, 1999, 2000 a, b) has proposed that chewing food well from infancy will lead to a clear-headed and robust person, following which the same concept has been presented to the general public by the mass media. Unfortunately, however, there does not yet seem to be any direct evidence to support this claim. It is thus necessary to review mastication from the standpoint of the new concept of evidence-based medicine (EBM) and to create a new direction in medicodental research and treatment from the viewpoint of human evolution, because the causal relationship between mastication and brain function has never been clarified either in fossil science research or in the modem scientific bibliography. To confirm the human historical fossil record in regard to the causal relationship between the development of mastication and brain function in human evolutionary processes, the effect of gum chewing on brain reaction was examined in humans by means of a positron-emission tomography (PET) camera (Momose et al. 1997) after an antecubital intravenous injection of H215O. Powerful activation of the cortical cells was demonstrated in multiple cortical areas involving the marginal areas of the bilateral central sulci of the cerebral cortex (Fig. 1), and the activated areas coincided with our previous results in region of interest (ROI) analysis (Momose et al. 1887). Three-dimensionally, numerous cortical cells were shown to form nuclei on relief maps (Fig. 2). As diets and feeding habits changed in a stepwise manner from frugivorous to omnivorous via herbivorous and carnivorous over the lengthy progress of evolution, the brain concomitantly grew and the cranial capacity gradually increased in volume from 500 cm3, food from plant sources to animal sources (700 cm3), and then to both (1500 cm3), during the human evolutionary and developmental processes. Gradual increases in the cranial capacity of human fossils during the developmental stage have been demonstrated also by PET images of the human brain acquired by means of a PET camera and an antecubital intravenous injection of H215O during mastication that showed powerful activation of cortical cells in multiple areas. It could be concluded that human fossils give us concrete information on how to feed our children in the modern human life style from infancy to adulthood, so that we should bring children up by adhering to images of the principal feeding habits discovered during this research on human evolutionary and developmental processes.

Brain↗
PubMed2003

Central neurocytoma with craniospinal dissemination.

Central neurocytoma was first described by Hassoun et al. in 1982. The tumor is a rare benign tumor of the central nervous system, usually located in the lateral ventricles. Most reported cases are histologically and clinically benign. Several cases with recurrence have been described. Including the case presented here, only seven cases with craniospinal dissemination have been reported. None of the previous cases with dissemination had histological atypia but most did have a high MIB-1 labeling index (MIB-1 LI). Our patient had a high MIB-1 LI (4.6%) and dissemination was found to have advanced through the anterior horns of the lateral ventricles and to the spinal cord at the T4 level. The patient underwent partial resection of the tumor with follow-up radiation treatments for the residual tumor and dissemination. After the radiation, the size of the tumor decreased. The report of this casewill be helpful in the treatment of disseminated central neurocytoma.

Adult↗
PubMed2003

Hemangiomas in the face and extremities: MR-guided sclerotherapy--optimization with monitoring of signal intensity changes in vivo.

The feasibility of a method of magnetic resonance (MR)-guided sclerotherapy for hemangioma was evaluated. The distribution of a test injection and a contiguous sclerosant injection was monitored clearly with MR fluoroscopy. Postsclerotherapy T2-weighted MR images depicted areas with and those without effective sclerosant concentration, which enabled performance of selective supplemental sclerotherapy. This method of MR-guided sclerotherapy seems feasible for clinical application.

Adolescent↗
PubMed2003

[Simple visualization of the corticospinal pathway using tractography: one-ROI and two-ROI methods].

Diffusion tensor imaging (DTI), a magnetic resonance (MR) technique to analyze diffusion anisotropy of the brain, is able to demonstrate subtle white matter anatomy. Tractography is expected to be a unique, non-invasive tool to provide more pertinent insights into brain structure and orientation not accessible by conventional MRI. In this report, preliminary experiences of visualization of the corticospinal tract using tractography are described. DTI of the brain was performed in 5 normal volunteers using single-shot echo-planar imaging, then tractography was generated by our original software. We determined that the two-region-of-interest (ROI) method is superior to the one-ROI method.

Adult↗
PubMed2003

Simple quantification of skeletal muscle glucose utilization by static 18F-FDG PET.

UNLABELLED: Skeletal muscle glucose utilization (SMGU) can be measured by dynamic PET imaging with (18)F-FDG to characterize insulin resistance. The aim of this study was to determine the validity of simple methods to quantify SMGU by static PET imaging. METHODS: Ten patients underwent dynamic (18)F-FDG PET of the femoral region during hyperinsulinemic euglycemic clamping. SMGU was determined by Patlak graphical analysis using data from dynamic imaging with frequent arterial blood sampling. Standardized uptake values (SUVs) were calculated at 45 and 55 min after tracer injection. Skeletal muscle-to-background ratio (SM/B ratio), tissue count divided by venous plasma activity, was also computed at 45 and 55 min. These simple indices were compared by linear regression with the SMGU measured as above, and an estimated SMGU was obtained using the regression equation thus generated, together with a simple index. RESULTS: SMGU was highly correlated with SUVs (r = 0.941 at 45 min, r = 0.951 at 55 min) and SM/B ratios (r = 0.968 at 45 min, r = 0.984 at 55 min). Although SMGU was almost proportional to SM/B ratios, the y-intercepts of the regression lines for SUVs significantly differed from zero. The residual in estimating SMGU using the regression equation was marginally smaller for SM/B ratios than for SUVs and for indices at 55 min than at 45 min, but these differences did not reach statistical significance. Correction for plasma glucose level slightly elevated the correlation coefficients between SMGU and these simple indices. CONCLUSION: It is proposed that the simple quantitative indices, SUV and the SM/B ratio, are reliable indicators of SMGU during hyperinsulinemic euglycemic clamping. Static imaging with or without a single venous blood sampling may therefore be able to replace dynamic imaging with frequent arterial blood sampling, offering substantially greater convenience in evaluating insulin resistance.

Adult↗